Target security breach affects up to 40M cards

(AP) Target’s data-security nightmare threatens to drive off holiday shoppers during the company’s busiest time of year.

The nation’s second-largest discounter acknowledged Thursday data connected to about 40 million credit and debit card accounts was stolen as part of a breach that began during the Thanksgiving weekend.

The theft marks the second-largest credit card breach in U.S. history, exceeded only by a scam that began in 2005 involving retailer TJX Cos. and affected at least 45.7 million card users.

Target’s disclosure came a day after reports the company was investigating a breach.

Customers who made purchases by swiping their cards at its U.S. stores between Nov. 27 and Dec. 15 might have had their accounts exposed. The stolen data included customer names, credit and debit card numbers, card expiration dates and the embedded code on the magnetic strip on back of the card, Target said.

There was no indication the three- or four-digit security numbers visible on the back of the card were affected.

The data breach did not affect online purchases, the company said.

Target has not disclosed exactly how the breach occurred but said it fixed the problem.

Large companies spend millions of dollars each year on credit-card security measures. Given the company’s heavy security, the theft may have been an inside job, said Avivah Litan, a security analyst with Gartner Research.

“The fact this breach can happen with all of their security in place is really alarming,” Litan said.